text: A common example of use is finding the pressure inside an air bubble in pure water, where  = 72 mN/m at 25 °C (298 K).  The extra pressure inside the bubble is given here for three bubble sizes: 
  A 1 mm bubble has negligible extra pressure. Yet when the diameter is ~3 μm, the bubble has an extra atmosphere inside than outside. When the bubble is only several hundred nanometers, the pressure inside can be several atmospheres. One should bear in mind that the surface tension in the numerator can be much smaller in the presence of surfactants or contaminants.  The same calculation can be done for small oil droplets in water, where even in the presence of surfactants and a fairly low interfacial tension  = 5&ndash;10 mN/m, the pressure inside 100 nm diameter droplets can reach several atmospheres.